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Study finds PET scans can refine diagnoses of vegetative states

By Denise GradyNew York Times

Posted:
04/15/2014 12:01:00 AM CDT

Updated:
04/15/2014 09:31:13 PM CDT

People with severe brain injuries sometimes emerge from a coma awake but unresponsive, leaving families with painful questions. Are they aware? Can they think and feel? Do they have any chance of recovery?

A new study has found that PET scans may help answer these wrenching questions. It found that a significant number of people labeled vegetative had received an incorrect diagnosis and actually had some degree of consciousness and the potential to improve. Previous studies using electroencephalogram machines and MRI scanners have also found signs of consciousness in supposedly vegetative patients.

"I think these patients are kind of neglected by both medicine and society," said Dr. Steven Laureys, an author of the new study and the director of the Coma Science Group at the University of Liege in Belgium. "Many of them don't even see a medical doctor or a specialist for years. So I think it's very important to ask the question, are they unconscious?"

An article about the new research was published Tuesday in the Lancet.

Laureys and his colleagues studied 122 patients with brain injuries, including 41 who had been declared vegetative -- awake but with no behavioral signs of awareness. In the study, 81 other patients were considered "minimally conscious," meaning they showed intermittent signs of awareness and responsiveness. Such patients have a better chance of improving than those who are vegetative, although recovery may take a long time and be incomplete.

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Most of the patients were given brain imaging tests. PET scans measured brain activity in regions needed for consciousness, and the patients' results were compared with scans of healthy people. A lack of activity was interpreted as a vegetative state.

Some of the patients were also given a type of MRI scan used to measure brain activity while they were being told to imagine playing tennis or walking around their homes.

The imaging tests found minimal consciousness in 13 of the 41 vegetative patients. After a year, nine of the 13 had progressed into "minimally conscious states or a higher level of consciousness," the researchers said. Overall, PET scans were a better measure than MRI scans.

Researchers say the findings support the idea that within the pool of patients who appear vegetative are some who have some level of consciousness that they cannot show and the potential to recover.

But doctors caution that this type of PET scan is not widely available. Laureys also said the test might show signs of awareness in people who turn out to have little or no chance of meaningful recovery.